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arxiv: 2507.17656 · v2 · submitted 2025-07-23 · ❄️ cond-mat.str-el

Fragility of Topology under Electronic Correlations in Iron Chalcogenides

Younsik Kim , Junseo Yoo , Sehoon Kim , Sungsoo Hahn , Kiyohisa Tanaka , Li Yu , Minjae Kim , Changyoung Kim This is my paper

Pith reviewed 2026-05-19 02:34 UTC · model grok-4.3

classification ❄️ cond-mat.str-el
keywords iron chalcogenidestopological surface statesorbital-selective Mott phaseelectronic correlationsangle-resolved photoemission spectroscopyFeTe1-xSexZ2 topologysuperconductivity
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The pith

Non-trivial topology in iron chalcogenides loses observable surface-state coherence under strong electronic correlations.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper studies the effect of the orbital-selective Mott phase on topological surface states in FeTe1-xSex. Angle-resolved photoemission measurements show a doping-driven change from trivial to non-trivial Z2 topology between selenium fractions of 0.04 and 0.09. At higher temperatures the surface states lose coherence once the orbital-selective Mott phase appears, yet the underlying topological invariant is inferred to stay intact. The work therefore establishes that electronic correlations can render non-trivial topology fragile by suppressing its spectroscopic signatures without altering the bulk band topology itself.

Core claim

The non-trivial topology in iron chalcogenide is fragile under strong electronic correlations. Although the topological invariant remains unchanged, the coherence of the topological surface state deteriorates at elevated temperatures with the emergence of the orbital-selective Mott phase. A topological phase transition between trivial and non-trivial topology occurs as a function of selenium content between x = 0.04 and x = 0.09.

What carries the argument

Orbital-selective Mott phase that selectively suppresses quasiparticle coherence of topological surface states while leaving the bulk topological invariant intact.

If this is right

  • Selenium doping tunes a topological phase transition in FeTe1-xSex.
  • Topological surface states remain incoherent above the temperature where the orbital-selective Mott phase onsets.
  • The Z2 invariant itself is robust against the correlations that destroy surface-state visibility.
  • Strong electronic correlations can hide topological features in spectroscopy even when the underlying band topology persists.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same coherence loss may limit the visibility of topological states in other correlated iron-based compounds.
  • Experiments that suppress the orbital-selective Mott phase could restore coherent surface states at higher temperatures.
  • Theoretical descriptions of topology in these materials must include orbital-selective correlations to match the observed temperature dependence.

Load-bearing premise

The disappearance of surface-state signals is caused specifically by the orbital-selective Mott phase rather than ordinary thermal broadening or scattering, and the bulk topological invariant can be read reliably from the surface states without a direct calculation of the correlated bulk bands.

What would settle it

A direct computation of the Z2 invariant from the bulk bands in the high-temperature orbital-selective Mott phase, or the recovery of coherent surface states in a temperature window where the Mott phase is absent, would test whether the fragility claim holds.

Figures

Figures reproduced from arXiv: 2507.17656 by Changyoung Kim, Junseo Yoo, Kiyohisa Tanaka, Li Yu, Minjae Kim, Sehoon Kim, Sungsoo Hahn, Younsik Kim.

Figure 1
Figure 1. Figure 1: Crystal and electronic structure of FeTe1−xSex (FTS) (a) Crystal structure of FTS. (b) Schematic of the Brillouin zone of FTS. Blue and red dots at the time-reversal invariant momentum points indicate the even and odd parities of the bands, respectively. (c) First￾principles calculation of the projected band structure onto surface Brillouin zone along Γ − X. (d) First-principles cal￾culation of the band st… view at source ↗
Figure 2
Figure 2. Figure 2: Doping dependence of the electronic structures of FTS. (a-d) Band dispersion along Γ − X, recorded with a p-polarized 7 eV light at a temperature of 15 K, with selenium contents of x = 0.04, 0.09, 0.19, and 0.31, respectively. (e-h) Band dispersion along Γ − Z at 15 K, with selenium contents of x = 0.04, 0.09, 0.19, and 0.31, respectively. The yellow dashed lines and green dots represent the fitted peak po… view at source ↗
Figure 3
Figure 3. Figure 3: Temperature dependence of the electronic structures of FTS. (a-d) Band dispersion along Γ − X, recorded with p-polarized 7 eV light at temperatures of 15, 30, 50, 70 K, with a selenium content of x = 0.19, respectively. (e) Full width at half maximum of the Dirac surface state as (f-j) Band dispersion along Γ − Z with selenium contents of x = 0.09 at temperatures of 15, 30, 50, 70, and 175 K, respectively.… view at source ↗
Figure 4
Figure 4. Figure 4: Correlation and topology. (a) Schematic of band dispersion along Γ − Z. x1 and x2 denote the critical selenium contents in FTS where topological phase transitions occur. (b,c) Illustration of topological surface states at low and high temperatures. K, the mean free path estimated from the momentum width is less than 5 ˚A, which is strikingly short for a topologically protected surface state. Given that typ… view at source ↗
read the original abstract

The interplay between electronic correlations and topology is a central topic in the study of quantum materials. In this work, we investigate the impact of the orbital-selective Mott phase (OSMP) on the topological properties of FeTe1-xSex (FTS), an iron chalcogenide superconductor known to host both non-trivial Z2 topology and strong electronic correlations. Using angle-resolved photoemission spectroscopy, we track the evolution of topological surface states across various doping levels and temperatures. We identify a topological phase transition between trivial and non-trivial topology as a function of selenium content, with critical behavior observed between x = 0.04 and x = 0.09. Additionally, we find that at elevated temperatures, the coherence of the topological surface state deteriorates due to the emergence of OSMP, despite the topological invariant remaining intact. Our results demonstrate that the non-trivial topology in iron chalcogenide is fragile under strong electronic correlations.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript uses ARPES to study FeTe_{1-x}Se_x, reporting a doping-driven topological phase transition with critical behavior between x=0.04 and x=0.09. It further claims that at elevated temperatures the coherence of the topological surface states deteriorates due to the orbital-selective Mott phase (OSMP), while the Z_2 topological invariant remains intact, leading to the conclusion that non-trivial topology in iron chalcogenides is fragile under strong electronic correlations.

Significance. If the attribution to OSMP and the invariance of the topological index can be placed on firmer footing, the work would supply a concrete experimental illustration of how orbital-selective correlations can suppress surface-state coherence without destroying the underlying bulk topology. This would be relevant to ongoing efforts to understand the interplay between Mott physics and topological protection in iron-based materials.

major comments (2)
  1. [Discussion of temperature evolution and topological invariant] The assertion that the topological invariant remains unchanged at elevated temperature rests on inference from ARPES surface features alone. No direct evaluation of the Z_2 invariant (Wilson loop, parity analysis, or equivalent) is reported on the effective Hamiltonian or DMFT bands that exhibit the OSMP. This inference is load-bearing for the claim that topology survives while coherence is lost.
  2. [Temperature-dependent ARPES data and OSMP identification] The link between loss of surface-state coherence and the emergence of the OSMP is not isolated from generic thermal broadening or scattering. The manuscript presents temperature-dependent ARPES spectra across doping levels but does not include control comparisons (e.g., temperature series in the trivial-topology regime or quantitative modeling of scattering rates) that would establish specificity to the OSMP.
minor comments (2)
  1. [Doping-dependent results] The doping values at which the topological transition occurs (x = 0.04–0.09) are stated without reported uncertainties or details of how the surface-state gap closing was quantified.
  2. [Throughout] Notation for the selenium concentration (x) and for the orbital-selective Mott phase should be defined once and used consistently in all figure captions and text.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major comment below and indicate the revisions made.

read point-by-point responses

  1. Referee: [Discussion of temperature evolution and topological invariant] The assertion that the topological invariant remains unchanged at elevated temperature rests on inference from ARPES surface features alone. No direct evaluation of the Z_2 invariant (Wilson loop, parity analysis, or equivalent) is reported on the effective Hamiltonian or DMFT bands that exhibit the OSMP. This inference is load-bearing for the claim that topology survives while coherence is lost.

    Authors: We agree that a direct evaluation of the Z2 invariant on the DMFT bands would provide firmer support. Our inference relies on the ARPES observation of surface-state presence (and its doping dependence) together with the fact that the OSMP in these materials is known from theory to preserve the bulk band inversion without gap closure. We have expanded the discussion section to better articulate this reasoning and added citations to theoretical works that compute invariants in the correlated regime. We have not added new Wilson-loop calculations, as that would require substantial additional computational work beyond the scope of the current experimental study. revision: partial

  2. Referee: [Temperature-dependent ARPES data and OSMP identification] The link between loss of surface-state coherence and the emergence of the OSMP is not isolated from generic thermal broadening or scattering. The manuscript presents temperature-dependent ARPES spectra across doping levels but does not include control comparisons (e.g., temperature series in the trivial-topology regime or quantitative modeling of scattering rates) that would establish specificity to the OSMP.

    Authors: We acknowledge that generic thermal broadening must be ruled out. The temperature series are shown for multiple dopings, and the coherence loss occurs specifically in the doping window where independent measurements (transport, prior ARPES) establish the OSMP onset; in the low-x trivial regime the topological surface states are absent by construction, providing a natural contrast. We have added a quantitative analysis of MDC linewidths versus temperature, extracting scattering rates and comparing them to the expected OSMP temperature scale. This is now included in the revised manuscript and supplementary information. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental ARPES observations of surface-state evolution do not reduce to self-defined quantities or self-citation chains

full rationale

The manuscript is an experimental ARPES study that directly measures the temperature- and doping-dependent coherence of surface states in FeTe1-xSex and infers a topological phase boundary from the presence or absence of those states. No equations, fitted parameters, or derivations are presented whose outputs are then relabeled as predictions; the central claim that topology is fragile under OSMP follows from the observed loss of coherence at elevated T rather than from any algebraic identity or self-referential fit. Self-citations, if present, are not load-bearing for the reported fragility, and the topological invariant is discussed via experimental signatures rather than computed from a Hamiltonian that is itself defined by the same data. The work is therefore self-contained against external benchmarks and exhibits no reduction of results to inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on standard domain assumptions about Z2 topology and the orbital-selective Mott phase in iron chalcogenides; no new entities or free parameters are introduced in the abstract.

axioms (1)
  • domain assumption The topological invariant remains well-defined and unchanged even when surface-state coherence is lost due to the orbital-selective Mott phase.
    Stated directly in the abstract as the invariant remaining intact despite coherence deterioration.

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